Non-metallic tube stock usually is formed by laminating similar strips of paper or the like spirally upon a mandrel and gluing the strips to each other while feeding the required layers or laminae to the tube being formed until the desired thickness has been achieved. Meanwhile, the tube being formed continuously moves endlessly from the forming machine, whereby severing sections of the tube therefrom is necessary and desirable, the length of the tubes thus severed being controlled by the requirements of customers for the tubes.
Severing sections from a continuously formed non-metallic tube presents problems due to the fact that severing means must not only be advanced into the body of the tube to effect the severance but the severing means also must move longitudinally at the same speed as the tube and, after severance has been accomplished, the severing means must not only be retracted from engagement with the tube but also, very importantly, must be returned to a starting position for a repetition of the cycle.
In many manufacturing procedures at present, it is an objective to constantly increase the speed of production and the formation of tubes is no exception. By way of example, rather than limitation, it is quite common at present to form non-metallic tubes at speeds averaging from sixty thousand to seventy thousand lineal inches per hour, or approximately one thousand inches per minute. Cycles of operation per minute are dictated by the lengths of product required by a customer. Under circumstances, for example, such product tubes having a length of eight or ten feet, for example, will not require as frequent a cycle of operation of the cutting or severing means as when the product is much shorter, as for example, of the order of ten or twelve inches. When long lengths are produced, a severing machine having a single cutter operated in a rectilinear manner is quite satisfactory, wherein the cutter is moved into the tube, travels with it to effect severing, retracts from the tube, and then returns to starting position. Examples of cutting devices of this type, which were developed many years ago, are exemplified in the following U.S. patents:
U.S. Pat. No. 964,162; Jenkins; July 12, 1910
U.S. Pat. No. 1,413,191; Roland; Apr. 18, 1922
U.S. Pat. No. 2,019,890; Burke; Nov. 5, 1935
In an attempt to produce relatively short lengths of a tube and cut such shorter lengths therefrom while the tube is advancing, prior attempts to accomplish this have included the use of a plurality of pairs of disc cutters, mounted on an endless chain, or radial arms on a rotating shaft, the cutting discs being freely rotated, and although in opposed pairs, no means were included to move the cutters toward each other for purposes of facilitating the cutting operation or otherwise. Typical examples of prior art devices of this type are found in the following U.S. patents:
U.S. Pat. No. 1,641,866; Roberts; Sept. 6, 1927
U.S. Pat. No. 1,740,430; Mudd; Dec. 17, 1929
U.S. Pat. No. 1,751,293; Sherman; Mar. 18, 1930
In order to facilitate the individual cutting of sections from a paper tube, it has previously been accomplished by moving pairs of disc cutters toward and from each other by mechanical means. Examples of such procedure are found in prior U.S. Pat. No. 1,953,205 to White et al, dated Apr. 3, 1934, and U.S. Pat. No. 2,723,705 to Collins, dated Nov. 15, 1955. In White et al, no means are illustrated for feeding the tube while the cutting occurs, and apparently, the tube is stationary during each cutting operation and then subsequently advanced. In Collins, only a pair of disc-like cutters are shown with no specific means being illustrated either for operating the same to advance the cutters into the tube or move the same along with the tube as formed.
Still other attempts to sever paper tubes while moving continuously from the forming machine have been developed in which not only are a plurality of cutters mounted for free rotation on shafts which are positively moved toward and from the tube to enhance the cutting operation, but said cutters are also moved with the tube and then withdrawn and retracted to starting position. Examples of this type of apparatus are found in prior U.S. Pat. No. 2,699,099 to Robinson, dated Jan. 11, 1955 and No. 3,540,333 to Johnson, dated Nov. 17, 1970. In Robinson, pneumatic means move the freely-rotatable disc cutters toward the tube to incise the same and hydraulic mechanism moves the cutters axially with the tube. In Johnson, three disc cutters are carried by a circular rotatable carrier wheel and a tightening cable moves the cutters against the tube as the carrier wheel moves axially with the tube as propelled by air cylinder means.
Not only have paper tubes been cut by the devices referred to hereinabove, but, in addition, metallic tubing, such as metal pipes have been cut by mounting disc cutters respectively on pivoted arms and employing a rotatable cam to progressively force the cutters into the body of the pipe and then such cam means relax and permit a spring to retract the cutters from the pipe. One example of such a device is found in U.S. Pat. No. 3,748,935 to Beauchet, dated July 31, 1973.
Although the prior art individually shows certain specific features embodied in the present invention, the employment of a pair of opposed saws which engage and cut a tube moving longitudinally at relatively high speed presents various problems which the invention has solved in ways not suggested by the prior art, details of which are set forth below.